Belemnites

Belemnites lived during the periods of Earth history
known as the Jurassic and Cretaceous.

Reconstruction of a 'living' belemnite.

Cross-section through a belemnite rostrum.

Belemnites were marine animals belonging to the phylum Mollusca
and the class Cephalopoda. Their closest living relatives are
squid and cuttlefish. They had a squid-like body but, unlike
modern squid, they had a hard internal skeleton. In the animal's
tail, this formed a bullet-shaped feature sometimes referred
to as a guard, but more correctly termed a rostrum (plural:
rostra). These are the parts which are normally found as fossils.

Belemnites take their name from the Greek word belemnon meaning
dart or javelin. The fossilised rostra were widely believed to
have been flung down as darts from heaven during thunderstorms
(thunderbolts). Some have a finger-like shape and, in folklore,
they have been called Devil's Fingers and St Peter's Fingers.

Belemnite.

One of the smallest belemnites, Neohibolites minimus is found in Cretaceous rocks of England. The rostrum is about 3 cm long.